This invention relates to liquid fuel dispensing equipment for automotive service stations or the like where liquid fuel such as gasoline is dispensed from fuel storage tanks to automotive vehicles or, in some instances, to small fuel containers; and it especially relates to vapor recovery systems for such equipment, which prevent the escape of hydrocarbon vapors to the atmosphere during the refueling process by drawing the vapors through a vapor return line associated with a flexible fuel hose.
More particularly, the invention relates to a device for removing liquid fuel resulting from condensation or splashback, for example, that may block the vapor return line.
Most liquid fuel dispensing equipment includes a pump connected to a fuel reservoir, a valved nozzle adapted to be inserted in the fill pipe of a vehicle fuel tank, and a flexible fuel hose connected between the pump outlet pipe and the valve nozzle. The apparatus also includes, in most cases, a vapor recovery system for preventing the escape of hydrocarbon vapors to the atmosphere.
Previous vapor recovery systems have included passages in the valved nozzle for collecting vapors from the vehicle fuel tank, and a vapor return line integral with the flexible fuel hose for delivering the vapors back to the fuel reservoir. Some systems use a vacuum pump for drawing vapors through the return line and others rely on vapor pressure in the fuel tank. Often, the return line is defined by the inner wall of an outer hose or sleeve and the outer surface of a smaller diameter flexible inner hose which constitutes the liquid fuel conduit.
The vapor return line, however, frequently becomes blocked with liquid fuel due to condensation of fuel vapors and/or splashback that occurs during the refueling operation. As a result, the vapor recovery system fails and hydrocarbon vapors escape to the atmosphere. Usually, the liquid fuel collects in the lowest portion of the flexible fuel hose, such as in a loop that forms between the ends.
One solution to this problem is a system wherein a suction tube is positioned in the vapor return passage (i.e., the passage defined by the inner wall of the flexible outer sleeve and the outer wall of the fuel tube), with one end that extends to the approximate low point in the conduit where liquid fuel collects. The other end of the suction tube extends to a suction-producing device integral with the nozzle.
The suction-producing device may include, for example, a venturi block connected in series with the liquid fuel conduit through which the fuel passes into the valved nozzle. The block defines a venturi throat and the other end of the suction tube is connected to a radial passage extending through the wall of the block to the venturi throat so that the pressure drop in the throat produces a suction in the tube. Accordingly, the collected liquid fuel is drawn through the suction tube into the venturi throat and dispensed through the nozzle with the normal fuel flow.
One disadvantage of this device, however, is that the suction tube is vulnerable to blockage by small particles within the fuel hose. Also, backflow may occur when the flow of liquid fuel through the venturi is shut off.
The device of the present invention resolves many of the difficulties and disadvantages described above and affords other features and advantages heretofore not obtainable.